Embolic filters with a distal loop or no loop

ABSTRACT

The invention provides a device for filtering emboli from blood flowing through a lumen defined by the walls of a vessel in a patient&#39;s body, comprising a filter element and a self-expanding radial element associated with the filter element. The filter element is expandable from a collapsed configuration when the filter element is restrained to an expanded configuration when the filter element is unrestrained. The filter element comprises a self-expanding material having pores. The filter element has proximal and distal portions and a central portion, and has a shape in the expanded configuration which defines a cavity having a proximal facing opening. The self-expanding radial element is distal of the filter element, and the self-expanding radial element is adapted to maintain the filter element centered in the lumen.

FIELD OF THE INVENTION

[0001] This invention relates to devices used in a blood vessel or otherlumen in a patient's body. In particular, the present invention relatesto devices for capturing emboli and particulate in a lumen.

BACKGROUND OF THE INVENTION

[0002] During vascular surgery or endovascular treatment of vesselsincluding thrombectomy, atherectomy, balloon angioplasty, and/or stentdeployment, debris such as plaque and blood clots can move from thetreatment site through a vein or artery and compromise the flow of bloodat a location removed from the treatment site. In particular, variousprotection systems have been developed to prevent such debris fromembolizing in the vessel. Distal protection devices include filters andocclusive devices (e.g., balloons) placed distally of the treatmentsite. Proximal protection devices include filters and occlusive devicesplaced proximally of the treatment site. In the case of filters, embolicollect within or on the filter. The filter with captured emboli istypically collapsed into a recovery catheter and the catheter withdrawnfrom the patient's body.

[0003] In prior art filters it has been found that incorrect radialposition of the filter within a body conduit can compromise theperformance of the filter. Specifically, if a portion of the filterabuts a vessel wall, then the area of the filter available forperforming the filtering function is reduced. Further, radial motion ofan elongate member can cause the filter to lose wall apposition andthereby defeat the intended embolic capture function of the filter.

[0004] Most filters are mounted onto elongate support members, and thefilters are comparatively flexible as compared to the elongate supportmembers to which they are mounted. Radial motion of the elongate supportmember is often a consequence of back and forth axial motion of theelongate support member in tortuous body conduits. Radial motion of theelongate support member can compress the filter, causing it to loseapposition to the conduit wall and thereby defeat the intended emboliccapture function. Control of elongate member radial position by use ofproximal loops is discussed in U.S. Ser. No. 09/628,212, filed Jul. 28,2000, entitled “Improved Distal Protection Device” and U.S. Ser. No.10/093,572, filed Mar. 8, 2002, entitled “Distal Protection DevicesHaving Controllable Wire Motion,” the contents of each of which arehereby incorporated by reference herein. Radial motion of the elongatesupport member can also press the filter against a conduit and reducethe area available for filtering emboli.

[0005] A need in the art remains for an embolic protection filter inwhich an elongate support member does not cause the filter to haveexcessive contact with a body conduit, thereby decreasing the filterarea available for performing the filtering function.

SUMMARY OF THE INVENTION

[0006] The invention provides an embolic protection filter in which anelongate support member does not cause the filter to have excessivecontact with a body conduit, thereby decreasing the filter areaavailable for performing the filtering function. The invention alsoprovides an embolic protection filter in which radial wire motion doesnot compromise filter wall apposition

[0007] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary andexplanatory and are intended to provide further explanation of theinvention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1A is a side view and FIG. 1B is a cross sectional view of aprior art filter deployed in a body conduit.

[0009]FIG. 2A is a side view and FIG. 2B is a cross sectional view of anembodiment of the invention showing a distal loop.

[0010]FIG. 3 is a side view of an embodiment of the invention showing adistal loop and a tether.

[0011]FIG. 4 is a side view of an alternate embodiment of a filter ofthis invention.

[0012]FIG. 5 is a side view of a no loop filter.

[0013]FIG. 6 is a side view of an alternate embodiment of a no loopfilter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The terms “distal” and “proximal” as used herein refer to therelative position of the elongate support member, catheters, and filterin a lumen. Thus, “proximal” refers to a location upstream from the“distal” position. That is, the flow of a body fluid, such as blood,moves from the proximal to the distal portions of the device.

[0015] The invention encompasses the use of any filtration device to bedeployed in a lumen or vessel of a patient. Although the examples relategenerally to filter protection devices deployed distal to a treatmentsite, the device can also be deployed proximal to a treatment site inconnection with interrupting or reversing flow through the vessel. Inthe case of a proximally deployed device, it will be advantageous toconstruct the device on a hollow elongate member so as to preserveaccess to the treatment site through the hollow member.

[0016] In a preferred embodiment, the distal protection system comprisesa catheter which is loaded with an elongate support member or guidewireabout which is disposed a distal protection filter. The elongate supportmember is structurally similar to a traditional guidewire in somerespects. However, it is not used as a means of navigating the patient'svascular system and, therefore, does not need to be provided with all ofthe features of flexibility and steerability as does a traditionalguidewire. With these differences in mind, the terms elongate supportmember and guidewire may be used interchangeably herein. A floppy tip(described further below) may be at the distal end of the elongatesupport member or guidewire. Typically, the filter is introduced into ablood vessel through an introducing catheter. Methods of introducingguidewires and catheters and the methods for the removal of such devicesfrom vessels are well known in the art of endovascular procedures. In atypical procedure using the device of this invention, the elongatesupport member and filter are loaded into an introducing sheath orcatheter and moved into the vessel and through the catheter to thetreatment site. Typically, this is done by advancing a first, orintroduction guidewire, through the vessel to the region of interest. Acatheter is advanced over the guidewire to the region of interest, andthe guidewire removed. Then the filter or other functional devicecarried by the elongate support member is advanced down a cathetersheath to the region of interest but within the catheter. The cathetersheath is withdrawn to deploy (expand) the filter at the region ofinterest. Alternatively, the filter is preloaded into a catheter andheld in place by an outer sheath of the catheter and they are togetheradvanced through the vessel to the region of interest without using aninitial guidewire. In this embodiment the catheter/filter combinationwill be used to navigate through the vessel to the region of interest.Then the catheter is withdrawn to deploy the filter. In a secondalternative, an introduction guidewire is advanced to the region ofinterest, and the filter (contained in a catheter) is advanced over theguidewire to the region of interest, at which point the catheter isremoved leaving the deployed filter near the region of interest on theguidewire. In this embodiment the filter is not comprised of an elongatesupport member as previously defined, and the guidewire and/or filtermay be configured to preserve a spatial relationship between theguidewire and the filter. For example, the guidewire may be configuredto prevent the filter from advancing beyond the distal end of theguidewire.

[0017] In other embodiments of the invention, no catheter is requiredfor filter delivery. For example, the filter may be stretched axially soas to reduce its diameter to a size suitable for navigation through avessel and across a treatment site.

[0018] Typical dimensions of a filter used in the devices of thisinvention range from 2 mm to 90 mm in length, and from about 0.5 mm to 2mm in diameter before deployment, and from about 2 mm to 30 mm indiameter after deployment. A typical guidewire is about 0.2 to 1.0 mm indiameter and ranges from 50 cm to 320 cm in length.

[0019] The components of the distal protection system are made frombiocompatible materials. Materials also may be surface treated toproduce biocompatibility. The elongate support member may be formed ofany material of suitable dimension, and preferably comprises metal wire.Suitable materials include stainless steel, titanium and its alloys,cobalt-chromium-nickel-molybdenum-iron alloy (commercially availableunder the trade designation Elgiloy™), carbon fiber and its composites,and engineered polymers such as liquid crystal polymers,polyetheretherketone (PEEK), polyimide, polyester, and the like. A shapememory or superelastic metal such as nitinol is also suitable. Theelongate support member may be solid or may be hollow over some or allof its length.

[0020] The material used to make the filter or filter support structureis preferably self-expanding. Suitable materials include metals such asstainless steel, titanium and its alloys,cobalt-chromium-nickel-molybdenum-iron alloy (commercially availableunder the trade designation Elgiloy™), carbon fiber and its composites,and engineered polymers such as liquid crystal polymers,polyetheretherketone (PEEK), polyimide, polyester, silk, and the like. Ashape memory or superelastic metal is particularly suitable for thoseapplications when it is desired for an element, such as a filter, toassume a pre-determined three-dimensional shape or for a guidewire tomaintain a pre-determined curvature. A shape memory or superelasticmetal comprising nickel and titanium known as “nitinol” is commerciallyavailable in various dimensions and is suitable for use as both aguidewire and a filter. For example, nitinol tubular braid can be heatset into a desired shape, compressed for delivery to a site, and thenreleased to resume the heat-set shape.

[0021] The filter element has a body defining an interior cavity. Thefilter body has a plurality of openings or pores such that, when thefilter element is in its deployed configuration within the vessel lumen,fluid flows through the filter element and particles of the desired sizeare captured inside the interior cavity of the filter element.

[0022] The filter may comprise any material that is suitably flexibleand resilient, such as a mesh, i.e., a material having openings orpores. The filter may comprise braided, knitted, woven, or non-wovenfabrics that are capable of filtering particles, preferably having poresizes from 30 to 500 microns. Woven or non-woven fabrics mayadditionally be treated to fuse some or all of the fiber intersections.The fabric may be spun or electrospun. Suitable materials include thoseformed from sheets, films, or sponges, polymeric or metallic, with holesformed by mechanical means such as laser drilling and punching, or bychemical means such as selective dissolution of one or more components.For example, a suitable filter material is braided tubular fabriccomprising superelastic nitinol metal. Mesh fabric of nitinol materialcan be heat-set to a desired shape in its expanded configuration.

[0023] The material comprising the filter is preferably at leastpartially radiopaque. This material can be made radiopaque by plating,or by using core wires, tracer wires, or fillers that have good X-rayabsorption characteristics compared to the human body. Radiopaquefilters are described in U.S. patent application Ser. No. 10/165,803,filed Jun. 7, 2002, entitled “Radiopaque Distal Embolic ProtectionDevice,” the contents of which are hereby incorporated by referenceherein.

[0024] The embodiments of this invention, described in detail below inconnection with the figures, are suitable for use with various distalprotection systems that are known in the art. The filter may have awindsock type shape. The construction, deployment and retrieval of afilter having this shape is described, for example, in U.S. Pat. No.6,325,815 B1 (Kusleika et al.), the contents of which are herebyincorporated by reference herein.

[0025] The filter may also be a cup-shaped or basket-shaped device whichforms a proximally facing opening when expanded. The construction,deployment, and retrieval of such a filter is described in WO 96/01591(Mazzocchi et al.). This cup-shaped device may generally resemble anumbrella or a parachute, having a dome-like structure curving radiallyoutwardly from the guidewire or elongate support member. Other shapesmay be equally suitable in performing a filtering function, such as aconical shape, or a relatively flat disc shape. It will be appreciatedthat the shape of these filtration devices shown in various embodimentsare merely illustrative and are not meant to limit the scope of theinvention.

[0026] Regardless of the shape of the filter, the filter preferably isdeployed using an elongate support member. This can be done in variousways, and one or both of the proximal and distal ends of the filter maybe affixed to the elongate support member (by a fixed element) or may beslidably disposed about the elongate support member (by one or moresliding elements).

[0027] One type of sliding element comprises inner and outer annularrings. The first ring fits within the second ring. The inner diameter ofthe first ring is larger than the diameter of the elongate supportmember so that the sliding element can slide over the elongate supportmember. The sliding element can be affixed to the filter fabric byplacing the fabric between the first and second rings. However, this isnot meant to be limiting, and the filter fabric can also be affixed tothe sliding element by adhesive, solder, crimping, or other means knownin the art. The sliding element may comprise any stiff material such asmetal or polymer and preferably the slider is radiopaque. Suitablematerials include stainless steel, titanium, platinum, platinum/iridiumalloy, gold alloy, polyimide, polyester, polyetheretherketone (PEEK),and the like. Movement of a sliding element with respect to the elongatesupport member can be facilitated by coating one or both of the insideof the sliding element and the outside of the elongate support memberwith a friction-reducing coating, such as polytetrafluoroethylene or alubricious hydrophilic coating.

[0028] Fixed elements include annular rings. Also included within thismeaning is an element that is crimped, adhered, soldered, or otherwisefastened directly to the elongate support member. Also, the filterfabric may be attached directly to the elongate support member. In anyevent, the sliding and fixed elements (or any attachment point)typically comprise radiopaque material to assist in the placement of thefilter. In addition, one or more radiopaque markers may be positioned atvarious locations on the protection device. These radiopaque markers ormarker bands comprise a material that will be visible to X-rays and theyassist in positioning the device.

[0029] Some distal protection filters include a floppy tip at a distalportion of the guidewire or elongate support element. The floppy tipprovides an atraumatic and radiopaque terminus for the device. Anatraumatic tip prevents vessel injury during initial placement orsubsequent advancement of the device. A radiopaque tip helps thephysician verify suitable tip placement during fluoroscopy. The floppytip preferably comprises a springy or resilient material, such as ametal (e.g., stainless steel, iron alloys such as Elgiloy™, platinum,gold, tungsten, and shape memory or superelastic metal such as nitinol)or polymer (e.g., polyetheretherketone (PEEK), polyimide, polyester,polytetrafluoroethylene (PTFE), and the like). Springy materials aredesirable because they tend to retain their shape. The physician willinitially shape the tip, typically with a slight curve, and then as thedevice is advanced through the body the tip will be deflected as itencounters obstacles. It is desirable, after the inevitable deflectionsduring insertion, that the tip restore itself to the pre-set shape.Polymeric materials additionally may be reinforced with metals or otherfillers. The tip may be a monofilament or multifilament (such as acable). The floppy tip may be tapered or have a uniform diameter overits length. The floppy tip may comprise a tube, or could have circular,flat, or other cross-sections. It may be coiled. The tip may compriseone or more elements (for example, parallel independent structures). Thetip may be polymer-coated or otherwise treated to make the surfaceslippery. The floppy tip can be any desired length.

[0030] The filter comprises biocompatible materials such as metals andpolymeric materials. Materials such as metals and polymeric materialscan be treated to impart biocompatibility by various surface treatments,as known in the art. When wire is used, the wire is selected on thebasis of the characteristic desired, i.e., stiffness or flexibility, andthe properties can depend upon both the diameter of the wire and itscross-sectional shape. The size, thickness, and composition of elasticmaterials are selected for their ability to perform as desired as wellas their biocompatibility. It is to be understood that these designelements are known to one of skill in the art.

[0031] Filters are typically constructed as described in U.S. Pat. No.6,325,815 B1. See column 3, line 63, to column 4, line 16; and column 4,line 48, to column 5, line 36. The filter body typically comprises alength of a braided tubular fabric, preferably made of nitinol. Thefilter body is typically made by placing a braided tubular fabric incontact with a molding surface of a molding element which defines theshape of the desired filter body. By heat treating the braided tubularfabric in contact with the molding surface of the molding element, onecan create a filter body having virtually any desired shape.

[0032] Braiding is a process for producing a tubular interwovenstructure from individual strands. Braids are typically produced incontinuous lengths on commercially available braiding machines. Somecommercial products produced on braiding machines include rope,shoelaces, and reinforcing jackets for electrical cable. Medicalproducts produced by braiding include stents, vascular grafts, andcatheter reinforcing layers.

[0033] In a typical braiding process for making a 72 stranded braid,lengths of strands, such as wire, are wound onto bobbins. In thisexample 72 bobbins are wound with wire. Each bobbin is loaded into thecarrier of a 72 carrier braiding machine. Typically braiding machinesfor medical use have from 16 to 144 carriers or more. Each wire is ledthrough a tensioning mechanism in the carrier and all wire strands aregathered at a common central elevated position along the (typicallyvertical) axis of the braiding machine, where they are fastened to atake-up mechanism. The take-up mechanism may be a long mandrel arrangedalong the axis of the braiding machine and onto which the braid isformed during the braiding process. Once so configured, the carriers arerotated relative to the axis of the braiding machine. The carriers arerotated in a serpentine path, half of them moving clockwise and theother half moving counterclockwise, so as to interweave the strands in aprogrammed pattern. While the carriers are rotating, the take-upmechanism advances the woven braid in a direction away from thecarriers. The combination of these motions produces a helix of strandstwisting in a clockwise direction along the mandrel, interwoven with ahelix of strands twisting in a counterclockwise direction along themandrel. In this manner continuous lengths of braid are produced with aninside diameter of the braid equal to the outside diameter of thebraiding mandrel. The individual braid strands, while still on themandrel, can be twisted together after the length of the mandrel hasbeen braided. If desired, after removing the mandrel from the braidingmachine, the strands can be heat-treated. In the case of nitinolstrands, heat treatment on the mandrel at about 525° C. for 10 minutesor so can cause the nitinol-braided fabric to remember the shape andsize of the mandrel when the nitinol is at rest.

[0034] The average pore sizes of filters of the invention preferablyrange from 30 to 300 microns. In another preferred embodiment, theaverage pore sizes range from 30 to 150 microns. A pore size of about120 microns is preferred for devices intended to be used in connectionwith coronary procedures and a pore size of about 50 microns ispreferred for devices intended to be used in connection with carotid orintracranial procedures. The variation in pore size within the filtershould be minimized. In preferred embodiments of the invention, thestandard deviation of the pore size is less than 20 percent of theaverage pore size. In other preferred embodiments, the standarddeviation of the pore size is less than 15, 10, 5, or 2 percent of theaverage pore size.

[0035] The percent open area of the filters of the invention ispreferably greater than 50 percent. In other preferred embodiments, thepercent open area is greater than 60, 70, or 80 percent. A standardformula is used to calculate the percent open area of a given design.The percent open area is calculated by dividing the total pore area bythe total filter area (including the pore area).

[0036] The filters of the invention preferably are made of a materialhaving a tensile strength of greater than 70,000 psi (7031 kg/cm²), morepreferably greater than 150,000 psi (14,062 kg/cm²), and more preferablygreater than 200,000 psi (17,578 kg/cm²). Cast polymer films have amaximum tensile strength of about 10,000 psi (703 kg/cm²); orientedpolymer films have a tensile strength as high as 50,000 psi (3516kg/cm²), and metal filters typically contain wires having a tensilestrength of from 70,000 to 300,000 psi (7031 kg/cm² to 21,093 kg/cm²).

[0037] The various embodiments of the invention will now be described inconnection with the drawing figures. It should be understood that forpurposes of better describing the invention, the drawings have not beenmade to scale. Further, some of the figures include enlarged ordistorted portions for the purpose of showing features that would nototherwise be apparent. The material comprising the filter (e.g., mesh orfabric with pores, as described above) is omitted in the figures forsimplicity.

[0038] It is to be understood that the following embodiments are usefulfor any shape or type of filter. For example, these embodiments areuseful for any filter deliverable by any manner to a desired position ina body lumen where control of the desired characteristics of the filteras set forth above is desired. In particular, the invention includesboth proximal and distal filters.

[0039]FIG. 1A illustrates a prior art distal protection system in whichwindsock-shaped filter 10 is attached to elongate support member 15 viadistal sliding element 18. For clarity, the mesh of the filter is notdrawn in the figure. At the proximal end of the filter, proximal slidingelement 16 is slidably disposed about the elongate support member andattached to filter 10. Stop 12 is provided on the elongate supportmember in order to limit the relative motion of the filter along thesupport member. Support member 15 terminates distally at floppy tip 15b.

[0040] When deployed in a vessel V, filter 10 has wall appositionregions 11 at the proximal end of the filter and along the vessel wall.FIG. 1B shows filter 10 and wall apposition regions 11 in cross section.Fluid flow cannot pass through filter 10 in wall apposition regions 11because there is no space between the filter and the vessel in thisregion. In the case of a braided structure, flow cannot pass throughdistal portion of mesh 17 because the pores are generally very small.Most flow is confined to passing through the central portion 13 offilter 10.

[0041] Distal Loop Filters

[0042]FIG. 2A is a side view and FIG. 2B is a cross sectional view of anembodiment of the present invention. Windsock-shaped filter 20 isattached to elongate support member 25 via distal sliding element 28.For clarity, the mesh of the filter is not drawn in the figure. At theproximal end of the filter, proximal sliding element 26 is slidablydisposed about the elongate support member and attached to filter 20.Stop 22 is provided on the elongate support member in order to limit therelative motion of the filter along the support member. Stop 22 may be awire coil or a hypotube, polymer or metal, solid, or cut to improve itsflexibility. Stops and the use of stops are described in U.S. Ser. No.10/060,271, filed Jan. 30, 2002, entitled “Slidable Vascular Filter,”the contents of which are hereby incorporated by reference herein.Support member 25 terminates distally at floppy tip 25 b. Distal loop 24attaches to distal sliding element 28 and contacts vessel wall. Distalloop 24 may be made of elastic material such as metal or polymer andbiased to expand when unconstrained. Suitable materials include nitinol,stainless steel, ELGILOY™, polyimide, PEEK, liquid crystal polymer,polyester, and the like. If made of nitinol, the distal loop can be heatset to the desired expanded shape for example by heating to 525° C. forabout two minutes. When deployed in a vessel V, filter 20 has wallapposition regions 21 at the proximal end of the filter but not alongthe vessel wall distal of the proximal end. FIG. 2B shows filter 20 incross section, where it is apparent that wall apposition regions are notpresent as they are in FIG. 1B. In the case of a braided structure, flowcannot pass through distal portion of mesh 27 because the pores aregenerally very small. Most flow is confined to passing through thecentral portion 23 of filter 20, and this central portion 23 of filter20 is enlarged compared to prior art filters due to the effect of distalloop 24.

[0043] In FIG. 2, due to the effects of the distal loop, the wallapposition region of the filter is reduced compared to prior artfilters. However, the radial motion of the elongate support member 25wire can compromise the necessary wall apposition of the proximal end offilter.

[0044]FIG. 3 illustrates a windsock-shaped filter 30 attached toelongate support member 35 via distal sliding element 38. For clarity,the mesh of the filter is not drawn in the figure. At the proximal endof the filter, proximal sliding element 36 is slidably disposed aboutthe elongate support member and attached via tether 36 a to point 36 bon the filter 30. Stop 32 is provided on the elongate support member inorder to limit the relative motion of the filter along the supportmember. Stop 32 may be a wire coil or a hypotube, polymer or metal,solid, or cut to improve its flexibility. Support member 35 terminatesdistally at floppy tip 35 b. Distal loop 34 attaches to distal slidingelement 38 and contacts the vessel wall. Distal loop 34 can attach tothe proximal end, distal end, or at any point along distal slidingelement 38, and is configured so as to collapse into a catheter of lowprofile by incorporating hinges, zones of preferential bending, and thelike.

[0045] Tether 36 a reduces the influence of radial wire motion on thefilter mouth. Tether 36 a may be made of any strong biocompatibleflexible strand. Suitable materials include metal, polymer,monofilament, stranded, or cabled. For example, 0.004 inch (0.10 mm)diameter nitinol stranded wire made of 7 strands can be used. Morepreferably, 0.004 inch (0.10 mm) diameter 49 stranded nitinol cable canbe used. Stranded wire generally has more flexibility than monofilamentwire of the same overall diameter, and cabled wire generally has moreflexibility than stranded wire of the same overall diameter. Othersuitable materials include KEVLAR™ fiber, DACRON™ fiber, and othertextile fibers. Stainless steel wires, particularly in stranded orcabled form, may be preferred in some embodiments due to their highstrength. Further, it is desirable to coat the tethers with thrombosisreducing materials such as heparin to reduce clot formation on thetether.

[0046] By positioning elongate support member 35 such that there isslack in tether 36 a, the elongate support member can move laterallywithin the filter without compromising filter wall apposition. Tethersare more effective at accommodating lateral elongate member motion ascompared to the struts commonly used in prior art designs. It is alsoexpected that proximal sliding element 36 will slide to relieve tethertension in the event of lateral or radial elongate member motion,thereby preventing loss of filter apposition to a vessel wall. Struts,common in prior art designs, do not afford this degree of freedom foraccommodating elongate member motion. In addition, by locating elongatemember 35 within filter 30, lateral motion of the elongate member willtend to press filter 30 against the vessel wall because the filter wallis between the vessel and the elongate member. Further, good wallapposition of a given filter size is expected over a range of vesseldiameters because there is no stiff hoop at the opening of filter 30,rather, the filter mesh is gathered at connection 36 b. In contrast,many prior art designs have a stiff hoop at the proximal end of thefilter and such designs have difficulty accommodating a range of vesseldiameters due to the difficulty in collapsing the stiff hoop whilemaintaining close contact with the vessel wall.

[0047] This device can be deployed and used as follows. The proximal endof elongate member 35 is inserted into the distal end of catheter C(back loaded into catheter). Elongate member 35 is withdrawn proximallythrough catheter C causing stop 32 to contact slider 36, causing tensionto be applied to tether 36 a and resulting in filter 30 being drawn intocatheter C due to attachment of tether 36 a to filter 30 at point 36 b.Further proximal motion of the elongate member through catheter C drawsthe rest of filter 30, distal loop 34, and optionally floppy tip 35 binto catheter. The catheter with filter assembly therein is advanced toa region of interest and deployed nearby, generally distal of the regionof treatment in the embodiment shown in FIG. 3. Filter deployment isaccomplished by advancing filter 30 distally relative to catheter C. Ina preferred embodiment, filter 30 in catheter C is positioned distal toa treatment site, and catheter C is withdrawn proximally. Filter 30 willremain inside catheter C due to friction of filter against catheterwalls until distal sliding element 38 contacts stop 32. Catheter C willthen slide relative to filter 30, with reduced friction due to thetendency of filter 30 to elongate and reduce in diameter due to actionof stop 32 on distal sliding element 38. As catheter C is withdrawnproximally relative to filter 30, first distal loop 34, then filter 30will exit the catheter and expand to contact the vessel wall. Catheter Ccan then be withdrawn proximally and removed from the patient. At thispoint, treatment and diagnostic catheters can be introduced overelongate member 35. Excessive motion of filter 30 against the wall ofvessel V during catheter exchanges is prevented because sliders 36, 38allow axial and rotational motion between elongate member 35 and filter30. During treatment or diagnosis, emboli may be released from thetreated or diagnosed site and may be collected in the filter.

[0048] Alternatively, filter 30 can be front loaded into catheter C byintroducing floppy tip 35 b into the proximal end of catheter C andpushing elongate member 35 distally. Stop 32 will push against distalsliding element 38 and cause distal loop 34, filter 30, tether 36 a, andproximal sliding element 36 to enter into catheter C and advancedistally through catheter C. In this alternative, catheter C can beadvanced to a region of interest with the filter contained within. Morepreferably, a guidewire can be advanced to a region of interest,catheter C advanced to the region of interest over the guidewire, theguidewire withdrawn from catheter C, and filter 30 front loaded to theregion of interest and deployed as described above.

[0049] To recover the filter, catheter C is advanced over elongatesupport member 35 and the elongate support member is withdrawn intocatheter C. Stop 32 will abut proximal slider 36, and slider 36 coupledto tether 36 a coupled to filter 30 by way of point 36 b will causefilter 30 to be recovered into catheter C by continued proximal motionof elongate support member 35 relative to catheter C. Support member 35preferably should be withdrawn sufficiently to at least close theopening of filter 30; alternatively all or part of filter 30 and distalloop 34 may be withdrawn into catheter C. It is preferable to draw thedistal loop at least partially into catheter C so as to reduce oreliminate contact of distal loop with the vessel wall. At this time, thefilter/catheter combination can be withdrawn from the patient.

[0050]FIG. 4 illustrates an alternative embodiment of a filter of thisinvention in which windsock-shaped filter 40 is attached to elongatesupport member 45 via distal sliding element 48. At the proximal end ofthe filter, proximal sliding element 46 is slidably disposed about theelongate support member and attached via tether 46 a to point 46 b onthe filter. Point 46 b can be constructed in a manner similar to thatfor sliders 46, 48, or can be a structure such as a tube into whichtether 46 a and filter 30 are inserted and held together by crimping thetube, joining with adhesive, welding, or the like. Stops 42 a and 42 bare provided on the elongate support member in order to limit therelative motion of the filter along the support member. Stop 42 a isshown proximal to the filter opening and stop 42 b is shown within thefilter. Alternatively one stop, such as a wire coil or a hypotube,polymer or metal, solid or cut to improve its flexibility, can take theplace of stops 42 a and 42 b. Support member 45 terminates distally atfloppy tip 45 b. Distal loop 47 is affixed to distal sliding element 48.The distal loop serves to keep the filter open during movement of theelongate support member relative to the filter and to prevent theelongate support member 45 from moving radially and collapsing filter30. This is accomplished by keeping the elongate support member, whichslides through the distal sliding element 48, opposed to a vessel wall.A further advantage of distal loop stabilization of wire position isthat the distal loop does not impede entry of embolic particles into thefilter, unlike prior art approaches where struts and the like are oftenplaced proximal to the filter. Another advantage of a distal loop filteris that the mass of the loop and the comparatively large mass of theproximal filter do not overlap during collapse of these structures intoa delivery catheter, and as a result the profile of a delivery catheterfor the filter can be made smaller. Filter 40 can comprise metal orpolymer braid, polymer film with holes drilled therethrough, foams,other filter media as is known in the art, or any of the filter meshstructures disclosed in the U.S. patent applications filed on the samedate as the present application and entitled “Embolic Filters WithControlled Pore Size” (Atty Docket: EV31001 US) and “Embolic FiltersHaving Multiple Layers and Controlled Pore Size” (Atty Docket:EV31002US), the contents of each of which are hereby incorporated byreference herein.

[0051] No Loop Filters

[0052]FIG. 5 illustrates a distal protection system similar to thatshown in FIG. 4, but without the distal loop. Windsock-shaped filter 50is attached to elongate support member 55 via distal sliding element 58.At the proximal end of the filter, proximal sliding element 56 isslidably disposed about the elongate support member and attached viatether 56 a to point 56 b on the filter. Stop 52 is provided on theelongate support member between the distal and proximal elements. Thestop limits the relative motion of the filter along the support member.Support member 55 terminates distally at floppy tip 55 b which maycomprise a coil tip or any of the embodiments described earlier. Filter50 is comprised of any of the filter mesh structures disclosed herein.An advantage of a filter with no distal loop is that the mass of thefilter assembly is reduced, and as a result the profile of a deliverycatheter for the filter can be smaller. Further, no loop filters havefewer stiff structures associated with the distal end of the filter.These attributes allow no loop filters to cross tighter lesions and totrack more easily through tortuous vessels.

[0053]FIG. 6 illustrates a variation of the distal embolic protectionsystem shown in FIG. 5. Filter 60 is disposed about elongate supportmember 65 via distal sliding element 68 and is comprised of any of thefilter mesh structures disclosed herein. Stop 62 is provided on thesupport member and tether 66 a is attached to the distal end of the stop(at point 62 a) and the proximal end of the filter (at point 66 b),although the tether could be attached to either end of the stop or atany point therealong. The stop/tether structure limits the relativemotion of the filter along the support member and provides for radialmotion of the elongate support member. Support member 65 terminatesdistally at floppy tip 65 b.

[0054] Although we have generally used siding elements to describe theinvention, one or more fixed element could take the place of the slidingelements.

[0055] While the examples given generally relate to distal embolicprotection filters it is envisioned that the invention can apply toproximal filters as well.

[0056] While the examples given generally relate to windsock shapedfilters it is envisioned that the invention can apply to filters ofnearly any shape including cups, plates, cylinders, ovoids, and others.Generally, the invention is best embodied in filters having an openingfacing towards the direction of flow so that emboli have a tendency toenter the filter.

[0057] The above description and the drawings are provided for thepurpose of describing embodiments of the invention and are not intendedto limit the scope of the invention in any way. It will be apparent tothose skilled in the art that various modifications and variations canbe made without departing from the spirit or scope of the invention.Thus, it is intended that the present invention cover the modificationsand variations of this invention provided they come within the scope ofthe appended claims and their equivalents.

What is claimed is:
 1. A device for filtering emboli from blood flowingthrough a lumen defined by the walls of a vessel in a patient's body,comprising: a filter element being expandable from a collapsedconfiguration when the filter element is restrained to an expandedconfiguration when the filter element is unrestrained, wherein thefilter element comprises a self-expanding material having pores, whereinthe filter element has proximal and distal portions and a centralportion, the filter element having a shape in the expanded configurationwhich defines a cavity having a proximal facing opening; and aself-expanding radial element associated with the filter element,wherein the self-expanding radial element is distal of the filterelement, and the self-expanding radial element is adapted to maintainthe filter element centered in the lumen.
 2. A device of claim 1,wherein the self-expanding radial element comprises a loop, and whereinthe loop is generally circular in shape.
 3. A device of claim 2, whereinthe self-expanding radial element has one loop.
 4. A device of claim 2,wherein the self-expanding radial element comprises two or more loops.5. A device of claim 4, wherein the self-expanding radial element hastwo loops.
 6. A device of claim 1, wherein the filter element isattached to the self-expanding radial element by a fixed or slidingelement.
 7. A device of claim 6, wherein the fixed or sliding element isa sliding element.
 8. A device of claim 1, further comprising anelongate support member and wherein the filter element is carried on aportion of the elongate support member.
 9. A device of claim 8, whereinthe filter element is attached to the elongate support member at thedistal portion of the filter element.
 10. A device of claim 9, whereinthe filter element is attached to the elongate support member at thedistal portion of the filter element by a fixed or sliding element. 11.A device of claim 10, wherein the fixed or sliding element is a slidingelement.
 12. A device of claim 9, wherein the elongate support member isattached to the filter element at the proximal portion of the filterelement.
 13. A device of claim 10, wherein the elongate support memberis attached to the filter element at the proximal portion of the filterelement.
 14. A device of claim 13, wherein the elongate support memberis attached to the filter element at the proximal portion of the filterelement by a sliding element.
 15. A device of claim 13, wherein theelongate support member is attached to the filter element at theproximal portion of the filter element by a single flexible tether. 16.A device of claim 1, wherein the self-expanding radial element isadapted to not significantly impede the flow of blood through the lumen.17. A device of claim 1, wherein the device does not comprise any otherself-expanding elements other than the self-expanding material havingpores and the self-expanding radial element.
 18. A device of claim 1,wherein the self-expanding radial element is made of nitinol wire.
 19. Adevice of claim 1, wherein when the self-expanding radial element is inits expanded configuration, the self-expanding radial element generallydefines a plane substantially perpendicular to the elongate supportmember.
 20. A device of claim 1, wherein when the filter element is inthe expanded configuration, the average pore size is from 30 to 300microns and the standard deviation of the pore size is less than 20percent of the average pore size.
 21. A device of claim 1, wherein whenthe filter element is in the expanded configuration, the filter elementhas a percent open area greater than 50 percent.
 22. A device of claim1, wherein when the filter element is in the expanded configuration, thefilter element has a percent open area greater than 60 percent.
 23. Adevice of claim 1, wherein when the filter element is in the expandedconfiguration, the filter element has a percent open area greater than70 percent.
 24. A device of claim 1, wherein when the filter element isin the expanded configuration, the filter element has a percent openarea greater than 80 percent.
 25. A device of claim 1, wherein theself-expanding material having pores has a tensile strength greater than70,000 psi.
 26. A device of claim 1, wherein the self-expanding materialhaving pores has a tensile strength greater than 100,000 psi.
 27. Adevice of claim 1, wherein the self-expanding material having pores hasa tensile strength greater than 200,000 psi.
 28. A device of claim 1,wherein the self-expanding material having pores is made of metal.
 29. Adevice of claim 1, wherein the self-expanding material having pores ismade of nitinol.
 30. A device of claim 1, wherein the self-expandingmaterial having pores comprises wires braided to form diamond-shapedpores.
 31. A device for filtering emboli from blood flowing through alumen defined by the walls of a vessel in a patient's body, comprising:a filter element being expandable from a collapsed configuration whenthe filter element is restrained to an expanded configuration when thefilter element is unrestrained, wherein the filter element comprises aself-expanding material having pores, wherein the filter element hasproximal and distal portions and a central portion, the filter elementhaving a shape in the expanded configuration which defines a cavityhaving a proximal facing opening; and an elongate support member,wherein the filter element is carried on a portion of the elongatesupport member, wherein the filter element is attached to the elongatesupport member at the distal portion of the filter element, and whereinthe elongate support member is attached to the filter element at theproximal portion of the filter element by a single flexible tether. 32.A device of claim 31, wherein the single flexible tether is attached tothe elongate support member by a fixed or sliding element disposed onthe elongate support member.
 33. A device of claim 31, wherein the fixedor sliding element is a sliding element.
 34. A device of claim 31,wherein the fixed or sliding element is a fixed element.
 35. A device ofclaim 33, further comprising a stop on the elongate support memberdistal of the sliding element.
 36. A device of claim 31, wherein thefilter element is attached to the elongate support member at the distalportion of the filter element by a fixed or sliding element.
 37. Adevice of claim 36, wherein the fixed or sliding element is a slidingelement.
 38. A device of claim 33, wherein the filter element isattached to the elongate support member at the distal portion of thefilter element by a second sliding element.
 39. A device of claim 34,wherein the filter element is attached to the elongate support member atthe distal portion of the filter element by a sliding element.
 40. Adevice of claim 35, wherein the filter element is attached to theelongate support member at the distal portion of the filter element by asecond sliding element.
 41. A device of claim 31, wherein the flexibletether is a metal wire with a diameter less than 0.30 mm.
 42. A deviceof claim 41, wherein the flexible tether has a diameter less than 0.20mm.
 43. A device of claim 41, wherein the metal wire is stranded wire.44. A device of claim 31, wherein the flexible tether is made of nitinolwire.
 45. A device of claim 31, wherein the flexible tether is made ofstranded nitinol wire.
 46. A device of claim 45, wherein the strandednitinol wire has a diameter less than 0.30 mm.
 47. A device of claim 45,wherein the stranded nitinol wire has a diameter less than 0.20 mm. 48.A device of claim 31, wherein the device does not comprise any otherself-expanding elements other than the self-expanding material havingpores.
 49. A device of claim 31, wherein when the filter element is inthe expanded configuration, the average pore size is from 30 to 300microns and the standard deviation of the pore size is less than 20percent of the average pore size.
 50. A device of claim 31, wherein whenthe filter element is in the expanded configuration, the filter elementhas a percent open area greater than 50 percent.
 51. A device of claim31, wherein when the filter element is in the expanded configuration,the filter element has a percent open area greater than 60 percent. 52.A device of claim 31, wherein when the filter element is in the expandedconfiguration, the filter element has a percent open area greater than70 percent.
 53. A device of claim 31, wherein when the filter element isin the expanded configuration, the filter element has a percent openarea greater than 80 percent.
 54. A device of claim 31, wherein theself-expanding material having pores has a tensile strength greater than70,000 psi.
 55. A device of claim 31, wherein the self-expandingmaterial having pores has a tensile strength greater than 100,000 psi.56. A device of claim 31, wherein the self-expanding material havingpores has a tensile strength greater than 200,000 psi.
 57. A device ofclaim 31, wherein the self-expanding material having pores is made ofmetal.
 58. A device of claim 31, wherein the self-expanding materialhaving pores is made of nitinol.
 59. A device of claim 31, wherein theself-expanding material having pores comprises wires braided to formdiamond-shaped pores.